1. Field of the Invention
The present invention relates to a conductive sheet, a capacitive touch panel, and a display device.
2. Description of the Related Art
As a display device of a multifunctional mobile phone (smartphone), a digital camera, or the like, a so-called touch panel on which various operations can be performed by touch with a finger has been widely used. In these devices, the display device has a small size, and recently, a touch panel has also been used in a large display device of a personal computer or the like. In particular, a mutual capacitive touch panel which can detect a plurality of places simultaneously (allows multi-touch) has become widespread.
In a touch panel, it is necessary that electrodes are made hard to be visually recognized by an operator and are excellent in conductivity. In a small touch panel, for example, indium-tin complex oxide (ITO) electrodes are used; however, in a case where ITO electrodes are used in a large touch panel, sufficient conductivity is not obtained and reduction in cost is difficult.
Accordingly, for example, as described in JP2011-059772A, electrodes which have a mesh pattern (mesh) with a plurality of linked cells formed by making thin metal wires intersect each other are used. In this case, since an opening is formed in each cell, the electrodes exhibit light transmittance, and for this reason, the electrodes are substantially transparent. There is also advantage in that the mesh made of metal is high in conductivity and can be provided at low cost.
As described in JP2012-243058A, for example, electrodes are laminated under and above an insulating layer, and accordingly, the lower electrode and the upper electrode are opposed to each other at a plurality of places through the insulating layer. Capacitance is generated between the respective opposing places, and if the touch panel is pressed with a finger, capacitance changes with the effect of the finger. A pressed point of the touch panel is detected from the amount of change at this time, and an issued operation command is determined.
JP2012-243058A also discloses that, in a touch panel using mesh electrodes, a cell pitch of an upper electrode (in JP2012-243058A, “reception electrode”) is made greater than a cell pitch of a lower electrode (in JP2012-243058A, “transmission electrode”), thereby increasing detection accuracy.